Dog Not Feeding Her Puppies

My beautiful Pit Bull had 7 healthy pups 3 weeks ago today. She has been a great new mother. However yesterday one of boobies has started to swell up. She seemed fine. But today I got home from work and it's very large, hard, and she seems in much pain and won't feed the pups. I applied a warm wet cloth to it and got her comfy. But she still won't feed them. She isn't wanting to eat as much, but will eat some and drink water still. Should I start bottle feeding the pups asap?